Methods, materials and apparatus for cleaning and inspecting girth gear sets

ABSTRACT

A one-step method of cleaning a girth gear set of a mill in preparation for inspection is provided, the method comprising: substantially emptying the mill; inching the gear; spraying a low, very low or non-Volatile Organic Compound (VOC) cleaning formulation at high pressure onto the gear, the cleaning formulation comprising a non-VOC aliphatic hydrocarbon solvent, an extreme pressure lubricant, a fretting wear lubricant, a non-ionic surfactant, and a mixture of non-VOC unsaturated fatty alcohols; and continuing to spray the low or very low VOC cleaning formulation on the gear for sufficient time for the formulation to clean the gear, thereby providing a so cleaned gear.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/243,919, filed on Jan. 9, 2019, which is a Continuation-in-Part ofInternational Patent Application No. PCT/CA2017/000172, filed on Jul.10, 2017, which claims the benefit of U.S. Provisional Application No.62/361,955, filed on Jul. 13, 2016. The above-identified priority patentapplications are incorporated herein by reference in their entirety.

FIELD

The present technology relates to a method and formulation for cleaninggirth gear sets and method and apparatus for then inspecting the gears.More specifically, the formulation is a low or very low volatile organiccompound (VOC) formulation that cleans quickly and is low cost. Cleaningcan be done at very low speed or at high speed.

Non-destructive testing follows directly with an eddy current array(ECA) probe or a phased array ultrasound probe. A rigid ECA probe isused for girth gears and includes accelerometers, an integralpositioning encoder and a multiplexer for improved accuracy. They mayalso be used for final inspection during the gear manufacturing process.A flexible ECA probe is used for pinion gears and includesaccelerometers. More specifically, the method uses a rigid eddy currentsensor array to assess the integrity of large ring (girth) gears and aflexible ECA probe to assess the integrity of pinion (helical) gears onsite and in situ. The device and method are especially useful for piniongears.

BACKGROUND

All processing facilities that use Girth Gear Driven Mills, such as themining, pulp and paper and cement industry, use large gears. Forexample, the girth gear has straight cut teeth and is about 3 m to about14 m in diameter. The pinion gear drives the girth gear. It is muchsmaller, at about 0.5 m to about 2 m diameter. It has helix angles onthe gear teeth. These gears cannot be readily removed and transportedfor testing.

Methods of examining large girth gear teeth to detect surface breakingdiscontinuities have often been time-consuming and limited in terms ofdata collected. Methods such as visual and magnetic particle inspectionand liquid penetrant testing requires up to 24 hours to clean the gear,resulting in down time of up to 40 hours. These methods can misscritical discontinuities.

Typically, a gear could be inspected as frequently as every six monthsor as long as every two years, usually dependent on the insurancecompany's recommendations, which are based on their risk assessment.Hence, there are no personnel dedicated to conducting the testing. Asthese gears cost as much as 400,000 to 1.3 million dollars, an incorrector inaccurate inspection result can cost the mining, cement or pulp andpaper company a significant amount of money. Further, if there is afailure of the gear, this can lead to significant down time. For acopper-molybdenum, gold, iron ore mine this can be in the range of$20,000 to $100,000 an hour. It normally takes a minimum of 10 to 12days to change out a gear set, if there is one on site. If not, it couldtake up to 45 weeks for a replacement. A catastrophic failure in thesegear sets could cost the insurer millions of dollars.

These large gears need to be cleaned prior to inspection or maintenance.During part of the cleaning process, the mill cannot be used, andtherefore the longer the process takes, the more down time there is.Most cleaning methods and inspection methods take between 10 and 12hours and can take as much as two days.

Chemical cleaning reduces the time to clean a gear. The earlier chemicalformulations included chemicals that are dangerous to human health andenvironmentally unfriendly. For example, methylene chloride-basedsolvents were used. These are toxic to both the environment and tohumans. VOCs, such as most petroleum distillates, have also been used.While these are not as toxic as methylene chloride, they are stillconsidered to be dangerous to work with and are environmentally unsafe.

Another deficiency in the prior art chemical cleaning methods is thatthe gear teeth were rinsed with water based detergents or water. Duringthe rinsing, the gear teeth, as they rolled through mesh, were subjectedto metal to metal contact. This led to scuffing and micro-pitting,eventually leading to potential gear teeth cracking and eventuallyfailure.

A formulation and method for cleaning girth gears is disclosed in U.S.Pat. Nos. 5,031,648 and 5,146,938. The method is a two-step methodinvolving spraying a thixotropic formulation on the gear while the gearis in operation. The composition comprises at least one terpene beingcapable of dissolving or softening hardened lubricants and residuals,hydrocarbon solvent, an extreme pressure lubricant and surfactants. Themethod for cleaning mill gears comprises applying a solution comprisingat least one terpene being capable of dissolving or softening soilscontaining grease or oil, aliphatic hydrocarbon solvent, biodegradablesurfactants, an extreme pressure lubricant and thickeners to the area tobe cleaned, continuously applying the solution to contact the surfaceand penetrate and dissolve the surface grease, and thereafter rinsingthe surface to remove the dissolved surface greases and the cleaningcomposition. The initial spraying is carried out during production, withthe mill gear operating at full speed, followed by rinsing or wiping asthe mill gear is inched. The composition dissolves gear lubricant(Asphaltic) accumulations effectively and in an environmentallyacceptable manner as well as a method of cleaning mill gears resultingin significant savings in terms of labor and downtime of the equipment.The solution is safe to use on painted surfaces and emulsifies quicklywhen sprayed with water-soap solutions. The hydrocarbon solvent includesmineral spirits, which, in the commercial embodiment, Traxol®, is amiddle petroleum distillate, which is classified as a VOC. As disclosed,the hydrocarbon solvent also includes aromatics, which are both VOCs andcarcinogenic. The preferred terpene is d-limonene. The resultingformulation has a relatively low flash point of 142° F. and is a VOC.The formulation does not work well on synthetic lubricants. Theformulation is sprayed on the gear for about 1.5 to 2 hours, hence alarge amount of the formulation is required (600-800 litres). Rinsing isdone with a detergent-water solution. During the rinsing the gear isinched. This step takes approximately 20 to 30 minutes. During thistime, there is no protection for the gear as there are no additives inthe rinse solution and as a consequence, this method has been found todamage the gear teeth.

Eddy current technology is a widely used for quality control testing onobjects such as wire, rods or tubes. This testing often involves havingthe test objects travel along a work path, passing through eddy currentprobe(s). The operators are competent as they routinely conduct tests.

Eddy current testing can be performed on discs and other shaped objectsconstructed of conductive and/or non-magnetic materials to look fordefects and wear. Eddy current testing may use eddy current coilsdesigned to generate a changing magnetic field that may interact withthe disc to generate an eddy current. Variations in the phase andmagnitude of the generated eddy current may be measured by measuringchanges to the current flowing in the coil. Alternatively, changes inphase and magnitude of the generated eddy current may be measured usinga second coil. Changes in the phase and magnitude of the generated eddycurrent may indicate one or more flaws in the discs, such as smallcracks that may lead to failures if not addressed. Due to their smallsize and rigidity, such probes make inspection of large discs and otherlarge components that have varying and multiple geometries difficult andtime-consuming, and therefore expensive.

Eddy current sensor arrays (ECA), or eddy current sensors have beenemployed to measure stress on airplane parts, for example, on thelanding gear, and to measure weights of components. For example, U.S.Pat. No. 8,237,433 discloses methods for monitoring of stresses andother material properties. These methods use measurements of effectiveelectrical properties, such as magnetic permeability and electricalconductivity, to infer the state of the test material, such as thestress, temperature, or overload condition. The sensors, which can besingle element sensors or sensor arrays, can be used to periodicallyinspect selected locations, mounted to the test material, or scannedover the test material to generate two-dimensional images of thematerial properties. Magnetic field or eddy current based inductive andgiant magneto-resistive sensors may be used on magnetizable and/orconducting materials, while capacitive sensors can be used fordielectric materials. Methods are also described for the use ofstate-sensitive layers to determine the state of materials of interest.These methods allow the weight of articles, such as aircraft, to bedetermined. The operators are competent as they routinely conducttesting.

Eddy current arrays, as opposed to eddy current sensors, can be used inproduction and inspection lines. For example, U.S. Pat. No. 8,264,221discloses an eddy current probe assembly suitable for inspecting a testobject with longitudinal shape, being passed through the assembly in theobject's axial direction during an inspection session, the probeassembly comprising multiple probe modules being disposed in a radialplane and with the modules partially overlaying on each other forming anIRIS structure encircling an inspection zone, wherein a movement inunison of each of the probe modules closer to or further away from thecenter of the inspection zone makes the inspection zone enlarged orcontracted. Spring tension is applied on each of the probe modules sothat constant lift-off is maintained between the probe modules and thetest surface.

Array of eddy current elements for each probe module and multiple layersof probe modules can be employed to achieve complete coverage of thetest surface. The radial cross-sectional shapes of the test objects canbe of round or polygonal. Again, testing is routine and therefore theoperators are competent.

Flexible ECA probes that are strap-like have been disclosed that lackany form of protective coating. These can be pressed into round-edgedshapes, for example, pipeline, tube inspection, and aircraft. However,they are only useful for assessing wear and integrity of smooth surfacesand are subject to wear if used on hard edges or rough surfaces.

A patent pending flexible probe array (FPA) configured in a glove thatcan be worn by an inspector has been disclosed (US Publication No.20160025682). The FPA conforms to the inspection surface and allowsinspection of a wide region with each scan of the array. With thisarrangement, the operator receives tactile feedback of surface profilechanges and is able to adjust the pressure on the FPA to accommodatechanging geometries. The FPA approach eliminates the need to maintainprobe alignment and the raster scanning needed with a conventionalprobe. The system has been successfully demonstrated at four operatingpower plants. A major deficiency is that it relies heavily on theproficiency of the user and therefore there is a risk of human error.Further, the results would vary from operator to operator as there is noaccurate feedback to the operator to ensure consistency betweenoperators. In addition, the scan coverage on the glove is very small.

In general, scan speed is an important parameter when inspecting usingECA. If scanning is too fast in relation to the sampling rate, theinspection may not be accurate. If scanning is too slow, again theaccuracy may be affected. For standard or custom surface array probes, apositioning encoder may be attached to the ECA probe to monitor thespeed and to record where indications are found. Such an encoder addsbulk and interferes with the probe when scanning is being conducted onthe root of a gear tooth.

The ECA systems include a multiplexer, which is built into theelectronic instrumentation or in the probe. The distance between theprobe and the multiplexer can result in crosstalk.

What is needed is a more environmentally friendly formulation and methodfor cleaning girth gears. The formulation would preferably not include aVOC aliphatic hydrocarbon solvent. Preferably, the formulation wouldhave a high flash point. Preferably, the method would be a one-stepmethod that could be done quickly and without significant runoff ofharmful chemicals. Preferably, the formulation would be able to removesynthetic and asphaltic lubricants. Preferably, the formulation wouldnot be classified as a dangerous good and therefore would be anunclassified product. Preferably, the cost of production of theformulation could be lowered by reducing the number of componentsneeded. Preferably the formulation would be a low or very low VOCformulation. Preferably, the method would be rinse-free. Preferably themethod would reduce or remove the potential for damaging the gear teeth.The method of inspecting the gears would preferably follow directlyafter cleaning the gears and would use an eddy current array probedesigned for gears. The method and ECA probe would be suited for fieldtesting to accurately and quickly identify anomalies or defects on thegear flank and root of the gear teeth, including, but not limited topits, scuffing, and cracks. The method would also preferably be usefulfor different shapes and sizes of gear teeth. For pinion gears, aflexible probe would be preferred. The probes (both rigid and flexibleprobes) would preferably be long lived and have a surface that was wearresistant. It would be preferred if the multiplexer was integrated intothe probe and the positioning encoder was embedded in the probe. Itwould be advantageous if the resulting data were sent to a computingdevice, analyzed, displayed in two or three dimensions (C-Scan), or bothand archived. It would be of more advantage if the system was able toidentify indications of a minimum of 3/16″ in accordance with thestandards of the American Gear Manufacturer's Association.

SUMMARY

The present technology provides a more environmentally friendlyformulation and method for cleaning girth gears. The formulationcontains a non-VOC aliphatic hydrocarbon solvent. The formulation has ahigh flash point. The method is a one-step method that can be donequickly and without significant runoff of harmful chemicals. Theformulation can remove synthetic and asphaltic lubricants. Theformulation is not classified as a dangerous good under theTransportation of Dangerous Goods Act (TDG) and is therefore anunclassified product. The cost of production of the formulation islower, as the method allows for a reduction in the number of componentsneeded. The formulation is a low VOC or very low VOC formulation. Themethod is rinse-free. The method reduces or removes the potential fordamaging the gear teeth. Inspection of the gears visually, or with anECA probe, a Phased Array Ultrasonic (PAUT) probe, an Ultrasonic probe,3-dimensional laser, an Alternating Current Field Measurement (ACFM)probe or Electromagnetic Acoustic Transducer (EMAT) can be doneimmediately after cleaning, with no need for additional steps.Inspections using Magnetic Particle or Dye Penetrant are preceded withrinsing with a detergent or wiping.

The ECA probe and method of ECA inspection is suited for field testingto accurately and quickly identify anomalies or defects on the gearflank and root of the gear teeth, including, but not limited to pits,scuffing, and cracks. The method can be useful for different shapes andsizes of gear teeth. For pinion gears, a flexible probe is preferred.The probes (both rigid and flexible) are long-lived and have a surfacethat is wear resistant. The multiplexer is integrated into the probe andthe positioning encoder is embedded in the probe. The resulting data aresent to a computing device, analyzed, displayed in two or threedimensions (C-Scan), or both and archived. The system is able toidentify indications of a minimum of 3/16″ in accordance with thestandards of the American Gear Manufacturer's Association.

In one embodiment, a method of cleaning one or more of a girth geartooth of a mill and a pinion gear tooth of the mill in preparation forinspection, the method comprising: spraying a low or very low VolatileOrganic Compound (VOC) cleaning formulation onto the gear tooth, thecleaning formulation comprising a non-VOC aliphatic hydrocarbon solvent,an extreme pressure lubricant, a fretting wear lubricant, a non-ionicsurfactant, and a mixture of non-VOC unsaturated fatty alcohols; andcontinuing to spray the low or very low VOC cleaning formulation on thegear tooth for sufficient time for the formulation to clean the geartooth, thereby providing a so cleaned gear.

In the method, spraying may be at high pressure as the mill is inched.

In the method, the high pressure may be about 1500 to about 5000 psi.

In the method, the mill may be inched between one to about threerevolutions.

In the method, the non-VOC aliphatic hydrocarbon solvent may behydrotreated light naphtha.

In the method, the low or very low VOC cleaning formulation may compriseabout 53% to about 70% w/w hydrotreated light naphtha, about 1% w/wnon-ionic surfactant, about 7% to about 17% w/w unsaturated fattyalcohols, about 0.5% to about 4% w/w fretting wear lubricant and about3% to about 14% w/w extreme pressure lubricant.

In the method, the formulation may further comprise about 9% to about15% w/w terpineol.

In the method, the formulation may further comprise about 10% GroupI-III base oil.

In the method, the formulation may comprise about 67% hydrotreated lightaliphatic naphtha, about 10% extreme pressure lubricant, about 13%terpineol, about 9% unsaturated fatty alcohols and about 1% non-ionicsurfactant.

The method may further comprise inspecting the so cleaned gear toothusing one or more of an Eddy Current Array (ECA) probe, a Phased ArrayUltrasonic (PAUT) probe, an Electromagnetic Acoustic Transducer (EMAT),an Alternating Current Field Measurement (ACFM) probe and a3-dimensional Laser Scanner.

In the method, the inspecting may use the ECA probe.

The method may further comprise monitoring a scan speed with the ECAprobe, the ECA probe including an at least one Micro Electromechanical(MEMS) accelerometer, a red, green, blue light source and a processor,the processor in electronic communication with the MEMS accelerometerand the red, green, blue light source.

In the method, the so cleaned gear tooth may be a girth gear tooth andthe ECA probe may be a rigid ECA probe.

In the method, the so cleaned gear tooth may be a pinion gear tooth andthe ECA probe may be a flexible ECA probe.

In another embodiment, a method of examining an at least one girth geartooth on site is provided using a system comprising a rigid eddy currentsensor array probe in electronic communication with a computing device,the computing device having a processor and a memory, the memory toprovide instructions to the processor, the rigid eddy current sensorarray probe including a housing, a sensor layer retained in the housing,a resilient surface retained on the sensor layer, and a sensor zone inthe sensor layer proximate the resilient surface, and comprising aseries of drive coils and a series of sensing coils, the methodcomprising: standardizing the eddy current sensor array probe with areference standard; scanning the at least one gear tooth with analternating current; sending a data set to the computing device; thecomputing device analyzing the data set; and the computing devicedisplaying one or more of a two or three-dimensional image of the dataset on a user interface.

In the method, the resilient layer may be a removable Ultra HighMolecular Weight adhesive-backed plastic film and the method may furthercomprise assessing wear of the resilient layer and, if worn, replacingthe resilient layer.

The method may be conducted in the absence of re-standardizing the rigideddy current sensor array probe.

The method may further comprise the computing device archiving the dataset.

The method may further comprise multiplexing the data set.

In the method, a plurality of gear teeth may be examined for a surfacediscontinuity.

In the method, on site may be a mine site.

In another embodiment, a method of examining an at least one girth geartooth on site is provided using a system comprising a rigid eddy currentsensor array probe in electronic communication with a computing device,the computing device having a processor and a memory, the memory toprovide instructions to the processor, the rigid eddy current sensorarray probe including a housing, the housing retaining: an at least oneMicro Electromechanical (MEMS) accelerometer; a red, green, blue lightsource; a processor, the processor in electronic communication with theMEMS accelerometer and the red, green, blue light source; and a sensorlayer, a resilient surface retained on the sensor layer, and a sensorzone in the sensor layer proximate the resilient surface, and comprisinga series of drive coils and a series of sensing coils, the methodcomprising: standardizing the eddy current sensor array probe with areference standard; scanning the at least one gear tooth with analternating current; sending a data set to the computing device; thecomputing device analyzing the data set; and the computing devicedisplaying one or more of a two or three-dimensional image of the dataset on a user interface.

In another embodiment, system for assessing integrity of a girth gear onsite is provided, the system comprising: a rigid eddy current sensorarray probe, the eddy current sensor array probe including a housing, asensor layer retained in the housing, a resilient surface retained onthe sensor layer, and a sensor zone in the sensor layer, the sensor zonecomprising a series of drive coils and a series of sensing coils, bothseries located proximate the resilient layer, a multiplexer incommunication with the series of sensing coils, a plurality of datachannels in communication with the multiplexer; a computing device inelectronic communication with the series of drive coils, the computingdevice including a processor and a memory, the memory to provideinstructions to the processor; and a user interface.

In the system, the resilient layer may be a removable Ultra HighMolecular Weight adhesive-backed flexible plastic film.

In the system, the series of sensing coils may be arranged in an atleast two rows, the at least two rows offset by a half of a coil.

In the system, the rigid eddy current array probe may further comprisean at least one Micro Electromechanical (MEMS) accelerometer, a red,green, blue light source and a processor in electronic communicationwith the MEMS accelerometer and the red, green, blue light source.

In yet another embodiment, a method of assessing integrity of a girthgear tooth in situ is provided, the method comprising using the systemdescribed above.

In the method, a plurality of gear teeth may be examined for a surfacediscontinuity.

In another embodiment, a low VOC or very low VOC cleaning formulationfor cleaning a girth gear set is provided, the cleaning formulationcomprising about 53% to about 68% w/w hydrotreated light naphtha, about1% w/w non-ionic surfactant, about 9% to about 19% w/w unsaturated fattyalcohols, about 2% w/w fretting wear lubricant and about 8% to about 10%w/w extreme pressure lubricant.

The cleaning formulation may further comprise a terpene alcohol.

In the cleaning formulation the terpene alcohol may be terpineol.

The cleaning formulation may comprise about 9% to about 15% w/wterpineol.

The cleaning formulation may further comprise about 10% hydrotreatedaliphatic naphtha oil.

In another embodiment, an ECA probe for inspecting at least one of agirth gear tooth and a pinion gear tooth is provided, the ECA probeincluding an at least one Micro Electromechanical (MEMS) accelerometer,a red, green, blue light source and a processor in electroniccommunication with the MEMS accelerometer and the red, green, blue lightsource.

In the ECA probe, the probe may be a rigid probe for inspecting thegirth gear tooth, the rigid probe including a housing, a sensor layerretained in the housing, a resilient surface retained on the sensorlayer, and a sensor zone in the sensor layer, the sensor zone comprisinga series of drive coils and a series of sensing coils, both serieslocated proximate the resilient layer, a multiplexer in communicationwith the series of sensing coils, a plurality of data channels incommunication with the multiplexer.

The ECA probe may further comprise a positioning encoder retained in thehousing.

In the ECA probe, the probe may be a flexible probe for inspecting thepinion gear tooth.

In yet another embodiment, method of cleaning and inspecting a girthgear set in situ is provided, the girth gear set including a girth gear,which has a plurality of girth gear teeth and a pinion gear, which has aplurality of pinion gear teeth, the cleaning comprising: spraying a lowor very low Volatile Organic Compound (VOC) cleaning formulation ontothe gear set, the cleaning formulation comprising a non-VOC aliphatichydrocarbon solvent, an extreme pressure lubricant, a non-ionicsurfactant, and a mixture of non-VOC unsaturated fatty alcohols; andcontinuing to spray the low or very low VOC cleaning formulation on thegear set for sufficient time for the formulation to clean the gear set,thereby providing a so cleaned girth gear and a so cleaned pinion gear;and the inspecting comprising standardizing each of a rigid eddy currentsensor array probe and a flexible eddy current sensor array probe with areference standard; scanning the girth gear teeth with an alternatingcurrent using the rigid eddy current sensor array probe; scanning thepinion gear teeth with an alternating current using the flexible eddycurrent sensor array probe; sending a data set from each probe to acomputing device; the computing device analyzing the data sets; and thecomputing device displaying two or more of a two or three-dimensionalimage of the data sets on a user interface.

In the method, the spraying may be at low pressure onto the gear set,which is in use.

In the method, the formulation may further comprise a fretting wearlubricant and the spraying may be at high pressure, on a mill turning atinching speed.

In yet another embodiment, a method of examining an at least one piniongear tooth on site is provided using a system comprising a flexible eddycurrent sensor array probe in electronic communication with a computingdevice, the computing device having a processor and a memory, the memoryto provide instructions to the processor, the flexible eddy currentsensor array probe including flexible layer, a sensor layer retained inthe sensor layer and a resilient surface retained on the sensor layer,the method comprising: standardizing the eddy current sensor array probewith a reference standard; scanning the at least one gear with analternating current; sending a data set to the computing device; thecomputing device analyzing the data set; and the computing devicedisplaying one or more of a two or three-dimensional image of the dataset on a user interface.

The method may further comprise monitoring a scan speed with the ECAprobe, the ECA probe including an at least one Micro Electromechanical(MEMS) accelerometer, a red, green, blue light source and a processor,the processor in electronic communication with the MEMS accelerometerand the red, green, blue light source.

In the method, the resilient layer may be a removable Ultra HighMolecular Weight adhesive-backed plastic film and the method may furthercomprise assessing wear of the resilient layer and, if worn, replacingthe resilient layer.

The method may be conducted in the absence of re-standardizing the rigideddy current sensor array probe.

The method may further comprise the computing device archiving the dataset.

The method may further comprise multiplexing the data set.

In the method, on site may be a mine site.

FIGURES

FIG. 1 is a schematic of the system of the present technology.

FIG. 2A is a schematic of the rigid probe of the present technology;FIG. 2B is a cross sectional view at line 2B in FIG. 2A.

FIG. 3 is a schematic of the flexible probe of the present technology.

FIG. 4 is a flow chart of the method of cleaning and inspecting a gear.

DESCRIPTION

Except as otherwise expressly provided, the following rules ofinterpretation apply to this specification (written description, claimsand drawings): (a) all words used herein shall be construed to be ofsuch gender or number (singular or plural) as the circumstances require;(b) the singular terms “a”, “an”, and “the”, as used in thespecification and the appended claims include plural references unlessthe context clearly dictates otherwise; (c) the antecedent term “about”applied to a recited range or value denotes an approximation within thedeviation in the range or value known or expected in the art from themeasurements method; (d) the words “herein”, “hereby”, “hereof”,“hereto”, “hereinbefore”, and “hereinafter”, and words of similarimport, refer to this specification in its entirety and not to anyparticular paragraph, claim or other subdivision, unless otherwisespecified; (e) descriptive headings are for convenience only and shallnot control or affect the meaning or construction of any part of thespecification; and (f) “or” and “any” are not exclusive and “include”and “including” are not limiting. Further, the terms “comprising,”“having,” “including,” and “containing” are to be construed as openended terms (i.e., meaning “including, but not limited to,”) unlessotherwise noted.

Recitation of ranges of values herein are merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range, unless otherwise indicated herein, and eachseparate value is incorporated into the specification as if it wereindividually recited herein. Where a specific range of values isprovided, it is understood that each intervening value, to the tenth ofthe unit of the lower limit unless the context clearly dictatesotherwise, between the upper and lower limit of that range and any otherstated or intervening value in that stated range, is included therein.All smaller sub ranges are also included. The upper and lower limits ofthese smaller ranges are also included therein, subject to anyspecifically excluded limit in the stated range.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe relevant art. Although any methods and materials similar orequivalent to those described herein can also be used, the acceptablemethods and materials are now described.

Theoretical Considerations:

Eddy currents are more concentrated at the surface and decreaseexponentially in intensity with distance below the surface of the metal.This effect is known as the “skin effect.” The depth at which eddycurrent density has decreased to about 37% of the surface density, iscalled the standard depth of penetration (d). At two standard depths ofpenetration (2d), the eddy current density has decreased to 1/e2 squaredor 13.5% of the surface density. At three depths (3d), the eddy currentdensity is down to only 5% of the surface density.

The depth of penetration is dependent on test drive frequency, as wellas, the test material's conductivity and magnetic permeability. Thedepth of penetration decreases with increasing frequency, conductivityand permeability. It is important to know the standard depth ofpenetration because for some testing (like flaw detection) theinspection should be conducted at a frequency that places the depth ofany likely flaws at 1d or less where eddy currents are strong.Similarly, in order to detect subsurface defects, and to test highlyconductive, magnetic, or thick materials, lower frequencies should beused. When making conductivity tests, the sample should be at least 3dthick so that changes in the thickness of the sample do not affect themeasurements. When electrical conductivity in IACS—(InternationalAnnealed Copper Standard) and permeability in Henry/mm are known, thestandard depth of penetration can be calculated.

Basic Concepts of Eddy Current Array

Eddy Current Array (ECA) technology provides the ability toelectronically drive multiple eddy current coils placed side by side inthe same probe assembly. Data acquisition is performed by multiplexingthe eddy current coils in a special pattern to avoid mutual inductancebetween the individual coils. Most conventional eddy current flawdetection techniques can be reproduced with an ECA inspection. With thebenefits of single-pass coverage, and enhanced imaging capabilities, ECAtechnology provides a remarkably powerful tool and significanttime-savings during inspections.

Multiplexing

Multiplexing is the process by which multiple analog message signals arecombined into one digital signal on a shared medium. When eddy currentarray data is multiplexed, the individual eddy current coils are excitedat different times, allowing the system to excite all of the coils inthe probe without ever exciting any two adjacent coils at the same time.An undesirable effect known as mutual inductance (magnetic couplingbetween coils in close proximity) is minimized with the use of aninternal multiplexing system to carefully program the exact time thateach coil is excited to transmit its eddy current signal. The signalsare then reassembled before being displayed as an image. In addition tothe enhanced imaging capabilities of multiplexed data, multiplexingallows any individual coil (data) channel to be analyzed afterinspection. Multiplexing allows an increased channel resolution,increased coil sensitivity (through the reduction of mutual inductance),and a reduced noise level. This ultimately leads to an improvedsignal-to-noise ratio.

Definitions:

Computing device—in the context of the present technology, a computingdevice is any device or instrumentation that has a processor ormicroprocessor for data acquisition and data analysis. It may beintegrated into a single device that also provides the eddy currentarray with alternating current of one or more suitable frequencies.

Low VOC—in the context of the present technology a low VOC content isabout 5% to about 8%.

Very low VOC—in the context of the present technology a very low VOC isless than about 5%, preferably less than about 4%.

Non-VOC—in the context of the present technology non-VOC can includeVOC-exempt components.

Detailed Description:

The formulation was developed to meet the requirements of being low VOCor very low VOC (in the present technology is less than 4%) or non-VOC,have a high flash point, be not be classified as a dangerous good,provide good cleaning power for girth gears and protect the gear fromscuffing and other damage. The formulation is terpene-free. In oneembodiment, the formulation contains up to 13% terpineol.

An extreme pressure additive is included in the formulation (see Tables1-4). Examples of suitable extreme pressure additives suitable for thepresent formulation include, but are not limited to Lubrizol 1038,Lubrizol EP additive Anglamol 6043® and Hitec® 350C.

A VOC-exempt hydrocarbon base oil is included in some embodiments. Thesecan be base oils in Group I, II or III.

A fretting/antiwear lubricant is included in some embodiments. Thepreferred contain phosphate, such as an alkyl phosphate amine or aphosphate ester, or its equivalent. Without being bound to theory, thefretting wear additive provides protection from micro-pitting and wear.

A non-ionic surfactant is included in the formulations. Without beingbound to theory, the surfactant improves miscibility of the componentsof the formulation and, in the situations where the gear is rinsed priorto inspection, with water. Other methods include rinsing with hot water,solvent, detergent or wiping.

A major component of the formulation is a VOC-exempt hydrocarbon-basedsolvent. Hydrotreated aliphatic light naphtha, for example, but notlimited to Shellsol® D80, or its equivalents are the preferred solvent.In order to meet the low VOC, very low VOC or non-VOC end product, thesolvent is preferably VOC-exempt. ShellSol D80 is a low viscosity,colorless solvent with a low aromatics content and a mild odor. Product,as produced, meets the volatile organic compound (VOC) exemptioncriteria and definition of Low Vapour Pressure-VOC as established inCalifornia Air Resources Board's Consumer Products Regulation; in the USEPA's National Volatile Organic Compound Emissions Standards forConsumer Products; and in the Model Rule for Consumer Products asadopted by the Ozone Transport Commission (OTC). Due to their lowvolatility and photochemical reactivity, these LVP-VOCs are fully exemptand non-reportable VOCs in calculations of the VOC contents of regulatedconsumer product categories.

In the preferred embodiment, unsaturated fatty alcohols are included inthe formulation. These typically have a hydrocarbyl chain length ofbetween 6 and 24 carbon atoms. In some embodiments, the unsaturatedfatty alcohols have the general structure ofR—CH.dbd.CH—(CH.sub.2).sub.7-CH.sub.2OH, wherein R is H orC.sub.2-C.sub.7 alkyl. In some embodiments, the unsaturated fattyalcohol may be an unsaturated alcohol such as 9-decen-1-ol or9-dodecen-1-ol. In the preferred embodiment, the unsaturated fattyalcohols are made as described in US Publication No. 20150274619 whichis incorporated by reference herein, in its entirety.

TABLE 1 Alternative embodiment formulation A for use in cleaning gears.Concentration % Flash Common Name (w/w) Point (° F.) VOC Hydrotreatedlight naphtha 70-80 176 NO Extreme pressure lubricant  8-10 83 NOUnsaturated fatty alcohols 10-20 212 NO High flash point non-ionic 1.0425 NO surfactant

TABLE 2 Alternative embodiment formulation B for use in cleaning gears.Concentration % Flash Point Common Name (w/w) (° F.) VOC Hydrotreatedlight naphtha 70-80 176 NO Extreme pressure lubricant  8-10 83 NOTerpineol 1-2 190 NO Unsaturated fatty alcohols  9-19 300 NO High flashpoint non-ionic 1.0 425 NO surfactant

TABLE 3 Exemplary embodiment formulation G for use in cleaning gears.Concentration % Flash Common Name (w/w) Point (° F.) VOC Hydrotreatedlight naphtha 65-80 (67)  176 NO Extreme pressure lubricant 8-10 (10) 83NO Terpineol 9-15 (13) 190 NO Unsaturated fatty alcohols 9-19 (9)  300NO High flash point non-ionic 1.0 (1) 425 NO surfactant

TABLE 4 Exemplary embodiment formulation L for use in cleaning gears.Concentration % Flash Common Name (w/w) Point (° F.) VOC Hydrotreatedlight naphtha 53-68 (58) 176 NO Extreme pressure lubricant  8-12 (11) 83NO Hydrotreated naphtha oil   10 (10) 284 NO Fretting wear lubricant0.5-2 (1)  172 ? Terpineol  9-15 (12) 190 NO Unsaturated fatty alcohols7-17 (7) 300 NO High flash point non-ionic 1.0 425 NO surfactant

TABLE 5 Exemplary embodiment formulation M for use in cleaning gears.Concentration % Flash Common Name (w/w) Point (° F.) VOC Hydrotreatedlight naphtha 53-68 (68) 176 NO Extreme pressure lubricant  8-12 (11) 83NO Fretting wear lubricant 0.5-2 (2)  172 ? Terpineol  9-15 (12) 190 NOUnsaturated fatty alcohols 7-17 (7) 300 NO High flash point non-ionic1.0 425 NO surfactant

The formulations were tested to determine which formulation provided thebest cleaning. The formulations were tested by placing 25 mL asphalticlubricant in 250 mL formulation. They were allowed to sit for 2 minutes.The combination was then vortexed for 30 seconds and then filtered. Theamount of residue (asphaltic lubricant) remaining in the filter wasweighed. A second test was done using synthetic lubricant. 25 mL of thesynthetic lubricant was placed in 250 mL formulation. This was allowedto sit for 2 minutes. The combination was then vortexed for 30 secondsand then filtered. The amount of residue (synthetic lubricant) remainingin the filter was weighed.

TABLE 6 Cleaning capability of formulations. Lubricant FormulationDissolved lubricant (wt %) Asphaltic A 96.0 ± 1.5 Asphaltic B 96.9 ± 1.2Asphaltic G 89.7 ± .74 Asphaltic L 81.5 ± 3.3 Synthetic A 49.4 ± 8.8Synthetic B 78.8 ± 0.6 Synthetic G 92.0 ± 2.0 Synthetic L 89.6 ± 0.6

Formulations G and L were tested for protecting the gear from scarringusing American Society for Testing and Materials (ASTM) D4172. This testmethod can be used to determine the relative wear preventive propertiesof lubricating fluids in sliding contact under the prescribed testconditions. Wear, weld point and seizure was measured using ASTM D2783,which relates to the ability of the formulation to protect the gearunder extreme pressure. They were compared with a high-VOC, commerciallyavailable product that is used as the mill is running at full operatingrevolutions per minute (15-20). Formulation G performed better than thecommercial product with regard to extreme pressure properties.

This suggested that a method could be developed that involved cleaningat inching speed (inching leads to a much higher impulse on the gearteeth as they press against the pitch line of the opposing teeth and cantherefore damage the gear). Formulation G was not quite as protective asthe commercial product with regard to relative wear preventativeproperties of the formulation in sliding contact. However, as notedbelow, the cleaning method used reduces the amount of sliding contact incomparison to standard methods from about 1350 to 2400 revolutions (1.5to 2 hours at 15-20 RPM) to two revolutions.

TABLE 7 Exemplary formulation G23C. Common Name Concentration % (w/w)Hydrotreated light naphtha 53-68 (59) Extreme pressure lubricant  3-14(13) Fretting wear lubricant 0.5-2 (2)  Base oil 10 Terpineol  9-15 (10)Unsaturated fatty alcohols 4-17 (5) High flash point non-ionic 1.0surfactant

The fretting wear lubricant contained phosphate esters. The base oil wasa Group II base oil. The inclusion of these two components led tosignificant improvements in the performance of the formulation withregard to protecting the gear during cleaning. This was tested usingASTM D2783 and ASTM D4172.

Cleaning of the gear with the formulations of the present technology canbe done in about an hour. The gear is inched during the cleaning, hencereducing the chance of damaging the gear. The formulation is sprayed onthe gear using high pressure (about 1000 to about 5000 psi, preferablyabout 2000 to about 3500 psi). The formulation blends with the normallubricant. The gear need only travel through one to three rotations,preferable two rotations, thus reducing the potential for damage to thegear teeth. For ECA, Electromagnetic Acoustic Transducer (EMAT),ultrasonics and Phased Array Ultrasonics (PAUT), inspection can occurwithout any further treatment of the gear (With Ultrasonics and PAUT acouplant needs to be used for the inspection). Formulation K leaves athin film on the gear, which enhances sliding of the probe over thesurface being inspected. The gears need not be rinsed or wiped aftercleaning, hence the method is rinse-free and is a one-step method.

Based on the results, formulation M will be expected to provide betterwear, weld point, load wear and scarring as well as good dissolvingcapabilities.

In an alternative embodiment, the gears are wiped or rinsed aftercleaning and inspected using Magnetic Particle or Dye Penetrantinspection.

In an alternative embodiment, spraying is done at low pressure while themill is in use.

In the preferred embodiment, inspection is done with ECA. With regard toinspecting the girth gear, as shown in FIG. 1, a rigid probe, generallyreferred to as 10, has a housing 12, an optional shoe 14, a sensor layer16, a resilient surface 20 and a sensor zone 18 within the sensor layer16 proximate the resilient surface 20. The sensor layer 16 is preferablyabout 2 to about 3 mm thick. The probe output is preferably a highfrequency, ranging from about 50 kiloHertz (kHz) to about 500 kHz. Theshoe 14, if present, is shaped to conform to the shape of the articlebeing tested. There are three probes for the girth gear—a small probe, amedium probe and a large probe. The resilient surface 20 is long wearingand resistant to scratching. The resilient surface 20 is preferably aplastic polymeric material, such as, but not limited toUltra-high-molecular-weight polyethylene (UHMW), High-densitypolyethylene (HDPE), poly vinyl chloride or similar, slippery plastic. Apreferred surface is a removable UHMW adhesive-backed flexible plasticor Teflon® film, which is about 0.10 to about 0.25 mm thick. It has alow coefficient of friction and a high abrasion resistance. If anon-adhesive resilient surface is employed, then it is glued to thesensor layer 16 with a releasable adhesive layer 22. This allows forreplacement of the resilient surface 20, as needed. The rigid probe 10also has a positioning encoder 26 embedded within it. Locating theencoder within the probe reduces the overall bulk of testing equipmentat the gear (the encoder is usually attached to the outside of the probeand makes scanning more awkward, thus more prone to error). The probe 10also has at least one and as many as three Micro ElectromechanicalSystem (MEMS) accelerometers 28 that are in electronic communicationwith an external computing device 30 and firmware or microprocessor ormicrocontroller 31 in the probe 10. The microcontroller quantizes theoutputs of the accelerometer. This allows the scan speed to bemonitored. Should the speed go above or below the accepted range ofscanning speed, which is selected by the user, an audible or visualsignal will be emitted. A red blue green (RBG) light source 29 on theprobe 10 is in electronic communication with the computing device 30 andindicates that the speed is too slow (blue), too fast (red) or withinrange (green) in response to feedback from the computing device 30 orprocessor 31.

The rigid probe 10 is in communication with the computing device 30, thecomputing device 30 having a processor 32 to receive instructions from amemory 34. The MEMS accelerometer 28 is also in communication with thecomputing device via the microprocessor 31. A software programmeanalyses the acceleration data and calculates velocity. Random noisecollected with the measurement data are filtered with a Kalman filter inthe software programme.

The computing device 30 is in electronic communication with a userinterface 36. The eddy current array probe 10 and computing device 30are used in the method of the present technology and are provided as asystem.

The rigid probe 10 is also in electronic communication with electronicinstrumentation 38 that is capable of energizing the coils 40 of thesensor zone 18 with alternating current of one or more suitablefrequencies and is capable of measuring changes in the impedance of eachcoil 40 in the sensor zone 18. The instrumentation 38 includes acapability to convert the impedance information into physical propertyvalues for the material under examination, including the lift-off ateach point in the B-scan or C-scan. The instrumentation 38 is inelectronic communication with the computing device 30. The lift-off canvary from about 0 mm up to about 3 mm to about 4 mm from the inspectedsurface.

As shown in FIGS. 2A and 2B, the sensor zone 18 is comprised of aplurality of sensors 24, embedded in the sensor layer 16. Each sensor 24has a plurality of coils 40 to form an eddy current array, generallyreferred to as 42. There are at least two rows of coils 40 offset byhalf a coil 40. The array 42 is designed to cover the surface to beanalyzed. There are drive coils 44 and sensing coils 46. There is also amultiplexer 48 in the housing 12, in or proximate the sensor layer 16.The signals from the eddy current array 42 pass through the multiplexer48 and then to data channels 50. A multiplexer 48 is used when thenumber of sensing coils 46 for impedance measurement is greater than thenumber of channels 50. It is housed in the housing 12. Returning to FIG.1, the probe 10 is powered by an electrical power cord 56. Communicationcables 58 allow for the electronic communications.

With regard to inspecting the pinion gear, as shown in FIG. 3, aflexible probe, generally referred to as 60, a flexible layer 66, asensor layer 68 and low friction protective layer 70, which ispreferably a Teflon® film of about 0.10 to about 0.25 mm thick. Theflexible layer 66, sensor layer 68 and low friction protective layer 70are an elongate strip. The low friction protective layer 70 has a lowcoefficient of friction and a high abrasion resistance. A preferredlayer 70 is a removable UHMW adhesive-backed flexible plastic or Teflon®film. The probe output is preferably a high frequency, ranging fromabout 50 kilo Hertz (kHz) to about 500 kHz. The flexible layer 66conforms to the shape of the article being tested. The flexible layer 66and sensor layer 68 are flexible and can be bent to the shape of thearticle being assessed. The flexible probe 60 also has at least one andas many as three Micro Electromechanical System accelerometers 28 thatare in electronic communication with an external computing device 30 andfirmware or microprocessor or microcontroller 31 in the probe 60. Themicrocontroller 31 quantizes the outputs of the accelerometer 28. Thisallows the scan speed to be monitored. Should the speed go above orbelow the accepted scan speed, which is selected by the user, an audibleor visual signal will be emitted. A red blue green (RBG) light source 29on the flexible probe 60 is in electronic communication with thecomputing device 30 and indicates that the speed is too slow (blue), toofast (red) or within range (green) in response to feedback from thecomputing device 30. An encoder 26 is attached to the probe 10.

The flexible probe 60 is in communication with the computing device 30,the computing device 30 having a processor 32 to receive instructionsfrom a memory 34. The MEMS accelerometer 28 is also in communicationwith the computing device via the microprocessor 31. A softwareprogramme analyses the acceleration data and calculates velocity. Randomnoise collected with the measurement data are filtered with a Kalmanfilter in the software programme.

The computing device 30 is in electronic communication with a userinterface 36. The eddy current array probe 60 and computing device 30are used in the method of the present technology and are provided as asystem.

The probe 60 is also in electronic communication with electronicinstrumentation 38 that is capable of energizing the coils 40 of thesensor zone 18 with alternating current of one or more suitablefrequencies and is capable of measuring changes in the impedance of eachcoil 40 in the sensor zone 18. The instrumentation 38 includes acapability to convert the impedance information into physical propertyvalues for the material under examination, including the lift-off ateach point in the B-scan or C-scan. The instrumentation 38 is inelectronic communication with the computing device 30. The electronicinstrumentation 38 houses a multiplexer 48.

An overview of the method is shown in FIG. 4. The method of inspecting agear takes about 8 hours. The method is used for detecting anomalies anddefects in the gears, such as, but not limited to indications,discontinuities and defects. The part to be assessed is cleaned 100. Areference standard is used to standardize 102 all the channels 30 of thearray 22. The probe 10, 60 is placed 104 on the surface of the part tobe assessed, and, in the case of the flexible probe, is molded 106 tothe surface as the surface is scanned 108 with an alternating current.Testing is done in situ. The addendum, dedendum and root of the gearteeth are all assessed. For the girth gears, the method and the systemof the present technology provide a solution to assessing such gearsbecause of the replaceable resilient layer, the presence of both theencoder and multiplexer in the probe and the accuracy and precisionprovided by the MEMS accelerometer. For pinion gears, the teeth of thegears are arranged in a helix. The angle of the teeth is between about 2degrees to about 15 degrees. Pinion gears are more difficult to assessbecause of the helix angle. For these gears, the method and the systemof the present technology provide a solution to assessing such gearsbecause of the flexibility of the probe 60, the protection and lowfriction afforded by the Teflon® film and the accuracy and precisionprovided by the MEMS accelerometer.

The scan speed is controlled 112 by the operator, and is monitored 114with the MEMs accelerometer 28. The RGB light source indicates 116whether the speed is within the correct range. If there are no defectsthe alternating current produces 118 a uniform magnetic field above thesurface. If there are defects, the alternating current leads 120 to anon-uniform magnetic field. The signal provides 122 position and depthinformation. This signal is then processed 124 by the processor 52 usinginstructions provided 126 by the memory 54 to provide 128 depth, lengthand position information with regard to cracks. Data can be analyzedfrom individual coil channels or for the entire surface. Athree-dimensional image is produced 130 and displayed 132 on the userinterface 55. The data are archived 134 in the memory 54 for futurereference. The probe 10, 60 will detect both subsurface and surfacediscontinuities, thereby providing a complete assessment of theintegrity of the gear. In the case of the rigid probe 10, the resilientlayer is examined 136 for wear and is replaced 138 as needed. There isno need for re-standardization as the resilient layer is preferably aremovable UHMW adhesive-backed flexible plastic film, which is providedas a standardized film of consistent thickness or, less preferably, is anon-adhesive resilient surface that is glued to the sensor layer with areleasable adhesive layer. The use of a replaceable resilient surfaceprovides three advantages. The first is that the resilient layer/surfaceis all that needs to be replaced, thus reducing the cost that isnormally associated with probe wear. The second is that there is no needfor re-standardization, as the layer/surface can be replaced when thewear is still within tolerance limits. The third is that the replacementdoes not alter probe performance, as it is a standardized thickness,therefore there is no need for re-standardization after replacement ofthe resilient layer/surface.

If desired, a magnetic particle examination can also occur. This is notessential as it does not provide any additional information, but allowsone to display a crack in a picture for a report.

Any inspection method is usually followed with a visual inspection toview the gear teeth for contact patterns to ensure that the gear set iscorrectly aligned. If the gear set is out of alignment, it is adjusted.

In another embodiment, inspection is done visually or with MagneticParticle or Dye Penetrant Inspection methods. For these methods, thegears need to be wiped.

Example 1

TABLE 8 Exemplary formulation G23F and G23G. Concentration ConcentrationCommon Name % (w/w) % (w/w) Hydrotreated light naphtha   53-68 (65.8)60.8 Extreme pressure lubricant 3-14 (5) 3-14 (10) Fretting wearlubricant 3.2 3.2 Base oil 10 10 Terpineol  9-15 (10) 10 Unsaturatedfatty alcohols 4-17 (5) 5 High flash point non-ionic surfactant 1.0 1.0

A first fretting wear lubricant which has dodecyl phenyl phosphate andabout 6% phosphorus, is added at 2% and a second fretting wear lubricantcompound containing ethyl-hexyl phosphate at about 39% to about 51% andabout 11% to about 12% phosphorus is added at 1.2%. These are both antiwear/fretting wear lubricants.

The formulations G23F and G23G will pass or perform well in the ASTMD5182 (FZG test), in addition to performing better than the commercialproduct with regard to extreme pressure properties.

While example embodiments have been described in connection with what ispresently considered to be an example of a possible most practicaland/or suitable embodiment, it is to be understood that the descriptionsare not to be limited to the disclosed embodiments, but on the contrary,is intended to cover various modifications and equivalent arrangementsincluded within the spirit and scope of the example embodiment. Thoseskilled in the art will recognize, or be able to ascertain using no morethan routine experimentation, many equivalents to the specific exampleembodiments specifically described herein. Such equivalents are intendedto be encompassed in the scope of the claims, if appended hereto orsubsequently filed.

The invention claimed is:
 1. A method of examining an at least one girthgear tooth on site using a system comprising a rigid eddy current sensorarray probe in electronic communication with a computing device, thecomputing device having a processor and a memory, the memory to provideinstructions to the processor, the rigid eddy current sensor array probeincluding a housing, a sensor layer retained in the housing, a resilientsurface retained on the sensor layer, and a sensor zone in the sensorlayer proximate the resilient surface, and comprising a series of drivecoils and a series of sensing coils, the method comprising: cleaning theat least one girth gear tooth to expose a surface to be examined;standardizing the eddy current sensor array probe with a referencestandard; scanning the surface to be examined of at least one gear toothwith an alternating current; sending a data set to the computing device;the computing device analyzing the data set; and the computing devicedisplaying a three-dimensional image of the data set on a userinterface.
 2. The method of claim 1, further comprising examininganother at least one girth gear tooth in the absence of re-standardizingthe rigid eddy current sensor array probe.
 3. The method of claim 2further comprising the computing device archiving the data set.
 4. Themethod of claim 3, further comprising multiplexing the data set.
 5. Themethod of claim 4, wherein a plurality of gear teeth is examined for asurface discontinuity.
 6. The method of claim 5, wherein the surfacediscontinuity is one or more of pitting, scuffing and cracks.
 7. Themethod of claim 6, wherein the method is rinse-free.
 8. The method ofclaim 1, further comprising examining an at least one root, an at leastone dedendum and an at least one addendum.
 9. The method of claim 8,wherein on site is a mine site.
 10. The method of claim 9, wherein themill is inched during cleaning.
 11. The method of claim 10, wherein themill is inched between one to about three revolutions.
 12. The method ofclaim 11, wherein the cleaning the at least one girth gear is byspraying a non-Volatile Organic Compound (non-VOC) cleaning formulationonto the gear tooth, the cleaning formulation comprising a non-VOCaliphatic hydrocarbon solvent, an extreme pressure lubricant, a frettingwear lubricant, and a non-ionic surfactant.
 13. The method of claim 12,wherein the spraying is at a pressure of about 2000 to about 5000 psi.14. A method of examining an at least one girth gear tooth on site usinga system comprising a sensor selected from the group consisting of anEddy Current Array (ECA) probe, a Phased Array Ultrasonic (PAUT) probe,an Electromagnetic Acoustic Transducer (EMAT), an Alternating CurrentField Measurement (ACFM) probe and a 3 dimensional Laser Scanner inelectronic communication with a computing device, the computing devicehaving a processor and a memory, the memory to provide instructions tothe processor, the method comprising: cleaning the at least one girthgear tooth to expose a surface to be examined; standardizing the sensorwith a reference standard; scanning the surface to be examined of atleast one gear tooth; sending a data set to the computing device; thecomputing device analyzing the data set; and the computing devicedisplaying a three-dimensional image of the data set on a userinterface.
 15. The method of claim 14, wherein the sensor is a rigidEddy Current Array probe.
 16. A system for assessing integrity of agirth gear on site, the system comprising: a rigid eddy current sensorarray probe, the eddy current sensor array probe including a housing, asensor layer retained in the housing, a resilient surface retained onthe sensor layer, and a sensor zone in the sensor layer, the sensor zonecomprising a series of drive coils and a series of sensing coils, bothseries located proximate the resilient layer, a multiplexer incommunication with the series of sensing coils, a plurality of datachannels in communication with the multiplexer; a computing device inelectronic communication with the series of drive coils, the computingdevice including a processor and a memory, the memory to provideinstructions to the processor; and a user interface.
 17. The system ofclaim 16, wherein the series of sensing coils are arranged in an atleast two rows, the at least two rows offset by a half of a coil.